1. Field of the Invention
The present invention relates to a glass crack prevention film-like layer and a plasma display device using the glass crack prevention film-like layer.
2. Description of the Related Art
As shown in FIG. 3, a related-art plasma display device includes a plasma display panel 31, a spacer 32, a transparent front panel 33, and a housing 34. The transparent front panel 33 is made of a glass substrate about 3 mm thick and disposed on a visual side of the plasma display panel 31 through a gap 320 formed by the spacer 32. The housing 34 receives the plasma display panel 31, the spacer 32 and the transparent front panel 33 therein. Because the transparent front panel 33 is disposed through the gap 320 in this manner, external impact force can be prevented from acting directly on the plasma display panel 31 and heat generated in the plasma display panel 31 can be restrained from being transmitted to the transparent front panel 33.
There is, however, a problem that an image is doubled because of refraction of light in the interfaces between an air layer made up of the gap 320 and the plasma display panel 31 and between the air layer and the transparent front panel 33. There is also another problem that the plasma display device becomes heavy in weight and high in cost because the transparent front panel 33 needs to have a thickness of about 3 mm to endure external impact force.
On the other hand, the prevent applicant has already proposed, in Unexamined Japanese Patent Publication No. Hei. 9-259770, a plasma display device including a plasma display panel, and a transparent protective substrate directly attached to a visual side of the plasma display panel through a heat-resistant transparent sheet with cushioning properties and firmly sticking properties. In the proposed display device, an excellent effect that the double image problem can be avoided is fulfilled because no air layer as shown in the related art is disposed on the visual side.
In this proposal, it is however difficult to attach the transparent protective substrate to the plasma display panel through a transparent sheet because a hard and thick glass or acrylic substrate is used as the transparent protective substrate. When a glass substrate is used as the transparent protective substrate, a problem in weight and cost of the glass substrate still remains unsolved. Moreover, it cannot be said safely that the proposal is sufficient in terms of shock resistance, because shock resistance is roughly judged by impact force (about 0.0294 J) given when a steel ball 3 g in weight is dropped from a height of 1 m. There is a further problem that the transparent protective substrate cannot be removed easily even in the case where the transparent protective substrate needs to be removed for recycling when the display device is disposed of.